The present invention relates to a metal pipe having an excellent dimensional accuracy with less run-out, which is suitably used for a development sleeve, a fixing roll, or a photosensitive drum for electrophotographic apparatuses or electrostatic recording apparatuses such as copying machines or printers, or a base body thereof, particularly, used for the development sleeve or a base body thereof.
In electrophotographic apparatuses or electrostatic recording apparatuses such as copying machines or printers, development has been performed by visualizing an electrostatic latent image formed on a latent image holder such as a photosensitive drum. According to one known development method, a developer (toner) is supported on the surface of a rotating sleeve in which a magnet roller is previously disposed, and the toner is supplied to the surface of a latent image holder by a so-called jumping phenomenon, to visualize an electrostatic latent image on the latent image holder. The jumping phenomenon is a phenomenon that the toner is flown from the surface of the sleeve, which is disposed in proximity to the surface of the latent image holder, onto the surface of the latent image holder by a magnetic force characteristic of the magnet roller. Further, there is known another method in which development is performed in a non-contact state that the surface, on which toner is supported, of a sleeve is spaced from the surface of a latent image holder by a specific gap like the above-described development method utilizing the jumping phenomenon, for example, a two-component development method using a two-component developer, or a magnetic brush development method of forming a magnetic brush with a developer (toner) between the surfaces of a sleeve and a latent image holder, and supplying the toner onto the latent image holder by bringing the magnetic brush into contact with the surface of the latent image holder.
The sleeve used for the above-described development methods has been produced by cutting a long-sized metal pipe body into a specific length, to obtain a raw pipe, and adjusting the surface state and the dimensional accuracy of the raw pipe by cutting and polishing the outer peripheral surface of the raw pipe.
By the way, with respect to the above-described development sleeve used for development mechanism portions of electrophotographic apparatuses or electrostatic recording apparatuses such as copying machines or printers, the dimensional accuracy thereof exerts a large effect on an image obtained by using the sleeve. According to the development method using the sleeve, as described above, development is performed by supplying toner from the surface of the sleeve onto an electrostatic latent image held on a latent image holder such as a photosensitive drum by utilizing the so-called jumping phenomenon in which the toner is flown from the surface of the sleeve, which is disposed in proximity to the latent image holder, to the surface of the latent image holder, or by bringing a magnetic brush of the toner formed on the surface of the sleeve into contact with the latent image holder. Accordingly, the sleeve and the latent image holder such as a photosensitive drum must be rotated with a gap between the surfaces thereof usually kept constant. If the gap between the surfaces of the sleeve and the latent image holder varies during development, the amount of toner supplied by the jumping phenomenon or magnetic brush correspondingly varies, resulting in an image failure such as inconsistencies in density.
For this reason, it is apparent that the dimensional accuracy of a sleeve exerts a large effect on an image formed by using the sleeve. In particular, to keep constant the gap between the surfaces of a rotating sleeve and a rotating latent image holder, it is very important to enhance both the roundness of the outer periphery of the sleeve and the straightness of the center axis of the sleeve. In this regard, according to the prior art, as described above, the surface state and the dimensional accuracy of a sleeve have been adjusted by cutting and polishing the outer peripheral surface of the raw pipe.
Such a prior art method, however, has failed to obtain a sleeve having a sufficient dimensional accuracy, and it has been required to further improve the dimensional accuracy of a sleeve, particularly, the roundness and straightness of the sleeve.
In addition to the above-described development sleeve, a base body of a photosensitive drum as a latent image holder or a fixing roll used for electrophotographic apparatuses or electrostatic recording apparatuses has been formed by a metal pipe produced by the same method as that of producing a metal pipe for the development sleeve. The dimensional accuracy of the metal pipe used for such a photosensitive drum or fixing roll also exerts a large effect on the performance of the photosensitive drum or fixing roll. Accordingly, it has been required to improve the dimensional accuracy of the metal pipe used for a photosensitive drum or fixing roll.
An object of the present invention is to provide a metal pipe excellent in dimensional accuracy, which is suitably used for a development sleeve, a fixing roller, or a photosensitive drum for electrophotographic apparatuses or electrostatic recording apparatuses such as copying machines or printers, or a base body thereof.
To achieve the above object, the present inventor has studied to improve the dimensional accuracy of a metal pipe used for a development sleeve or a base body thereof, produced by cutting a long-sized metal pipe body into a specific length, to obtain a raw pipe, and cutting and polishing the outer peripheral surface of the raw pipe, and has found that the dimensional accuracy, particularly, each of the roundness and straightness of the metal pipe is affected not only by the machining accuracy at the time of production of the metal pipe but also largely affected by physical properties of the raw pipe before being cut and polished, particularly, the inner stress characteristic of the raw pipe in the state being cut and polished, and that a metal pipe excellent in dimensional accuracy, particularly, excellent in roundness and straightness and thereby less in run-out can be certainly produced by cutting and polishing a raw pipe less in inner stress, and therefore, a high performance development sleeve excellent in dimensional accuracy can be obtained by using such a metal pipe excellent in dimensional accuracy.
On the basis of the above knowledge, the present inventor has measured physical properties of a raw pipe used for production of a metal pipe constituting a development sleeve and examined the effects of the physical properties of the raw pipe on the dimensional accuracy of the metal pipe produced by cutting and polishing the raw pipe, and found that the inner stress present in the raw pipe in the state being cut and polished is reduced after being cut and polished, that is, the stress remaining in the raw pipe is relieved by cutting and polishing, and thereby the dimensional accuracy adjusted by cutting and polishing is enhanced by relief of the inner stress.
As a result of further examination, the present inventor has found that a desirable dimensional accuracy of a metal pipe produced by cutting and polishing a raw pipe can be certainly obtained by setting the inner stress of the raw pipe in the state before being cut and polished to 20 N/mm2 or less, and therefore, a high performance development sleeve excellent in dimensional accuracy can be certainly obtained by using such a metal pipe, and eventually, the present inventor has accomplished the present invention.
Accordingly, the present invention provides a metal pipe produced by cutting a long-sized metal pipe body into a specific length, to obtain a raw pipe, and adjusting the surface state and the dimensional accuracy of the raw pipe by cutting and polishing the outer peripheral surface of the raw pipe, characterized in that the raw pipe has an inner stress of 20 N/mm2 or less.